Extraction is defined as a chemical or physical process for drawing out components of interest from a sample matrix. Traditional means of extraction involve mixing an extraction solvent with the sample matrix such that components of interest dissolve into the solvent in an attempt to achieve equilibrium based on the relative solubility of the sample matrix and the solvent. Solvent containing dissolved components can then be aspirated or otherwise removed for detection by a spectrographic device or injection into a chromatographic device.
Thorough mixing of the sample matrix and the solvent is important to maximize the contact between the sample matrix and the solvent. A number of improved methods for mixing include mechanical agitation, ultrasonic dissociation, shaking or stirring. Additionally, heating is sometimes employed to assist in the release of the components of interest. Depending on the complexity of the sample matrix undergoing extraction, it may take from several hours to several days to complete an extraction. The amount of a desired component extracted is dependent upon many variables including the extraction method used, complexity of the sample matrix and degree of mixing.